The present invention relates to an apparatus for assembling a piston assembly and a sub-assembly of a swash plate type compressor used, for example, in an air conditioner for an automobile.
In a swash plate type air compressor, a rotating shaft 2 having thereon a swash plate arranged at a predetermined angle relative to the shaft axis, as shown in FIG. 19, is generally used. Pistons 4 arranged in parallel relative to one another are incorporated in the rotating shaft 2 at positions (for example 5) equidistant in the circumferential direction around the peripheral edges 3a of the swash plate. The assembly consisting of the rotating shaft 2, the swash plate 3 and the pistons 4 is in general referred to as a "piston assembly P". The rotating shaft 2 of the piston assembly P is mounted, at each end, with a shaft bushing S, a race R, a bearing B and a thrust race S', and then inserted into an axial bore 5a and 6a of each cylinder 5 and 6 of a substantially cylindrical configuration, as shown in FIG. 20, so as to form a sub-assembly A shown in FIG. 23. It is noted that each piston 4 is received within bosses 5b and 6b of each of the cylinders 5 and 6 for slidable movement in the axial direction.
In the piston assembly P, each piston 4 is formed, at its central portion, with a notch 4a for receiving therein the peripheral edge 3a of the swash plate 3. A pair of shoes 7 for clamping therebetween the swash plate 3 in the axial direction are provided in each notch 4a. The shoes 7 are provided in order to reduce friction between the swash plate 3 and each piston 4. To this end, each shoe includes a spherical surface 7a adapted to be in contact with the wall of the notch 4a, and a flat surface 7b adapted to be in surface-to-surface contact with the front-side surface or rear-side surface of the swash plate 3.
With the construction mentioned above, and when the rotating shaft 2 is rotated, each piston 4 is urged by the rotating swash plate 3 and moved in one direction. Thus, the pistons 4 are reciprocally moved in the axial direction with a phase difference therebetween, so that a quantity of compressed air may be discharged.
When assembling the piston assembly P, an assembling jig 10 shown in FIG. 21 has been used in prior art. The assembling jig 10 includes a mount 11 having a round notch, formed through the upper surface toward the bottom surface thereof, for receiving the rotating shaft 2 having the swash plate 3 thereon, and a pair of support members 13 attached to the mount 11 at its upper portion on each side thereof for pivotal movement about a corresponding shaft 12 for open-close operation. The mount 11 is provided with three holding portions 11a of an arcuate cross-section at equidistant positions corresponding to the positions of the pistons 4. The holding portions 11a are intended to support thereon the pistons 4 which extend beyond the outer peripheral diameter of the swash plate 3.
The piston assembly P is assembled using the assembling jig 10 in the following procedure.
First, the support members 13 are pivoted about their respective shafts 12 to an open position, as shown by dotted line in FIG. 21. Then, three pistons 4 are disposed on the respective three holding portions 11a, with the bottom surfaces 4a' of their notches 4a facing the rotating shaft 2.
A pair of shoes 7 are placed on the bottom surface 4a' of the notch 4a of a first piston 4, with the shoes being in a laid position, i. e., with the spherical surface 7a being in contact with the bottom surface 4a' of the notch 4a. Then, the rotating shaft 2 is displaced downwardly, with the peripheral edges 3a of the swash plate 3 being engaged between the adjoining ends of the pair of shoes 7. By this, the shoes 7 are raised to a substantially vertical position by means of an urging force from the swash plate 3, so that the flat surface 7b of the shoes 7 are contacted respectively with the front-side and rear-side surfaces of the swash plate 3, as shown in FIG. 19.
Then, the support members 13 are pivoted about their respective shaft 12 in the direction shown by an arrow mark A in FIG. 21. Thereafter, the remaining two pistons 4 are assembled on the swash plate 3. When these pistons 4 are displaced downwardly, a pair of shoes 7 disposed in each notch 4a are urged upwardly by the swash plate 3 to a substantially vertical position, so as to clamp the swash plate 3 therebetween in the axial direction, as shown in FIG. 19. The two pistons 4 assembled are supported by the support members 13 in the lateral direction and prevented from dislodgement. It is noted that, during assembling the above two pistons 4, the shoes 7 in each notch 4a are held at a position by a finger(s) of an operator, so as to prevent them from dislodgement due to the gravity.
The thus assembled piston assembly P is put into the cylinders 5 and 6, by inserting each piston 4 into the boss 5b and 6b using another inserting jig.
It is noted, however, that, when using the abovementioned assembling jig 10, the bottom surface of the notch of each of the pistons disposed at the upper portion of the swash plate, so that the shoes of such pistons may be dislodged easily. Accordingly, significant time and skill are required, in order to perform a complete assembling of the pistons.
It is also noted that adherence of dust or the like to the swash plate may easily occur, since manual operation is still employed in the assembling process. Thus, variation in quality of the pistons assemblies would be caused, thus reducing the rate of operation of the entire assembling line.
Under the circumstances, the present invention is proposed to realize a fully automatic operation for assembling the pistons and shoes to the swash plate. The present invention also realize an automatic operation for inserting the piston assembly into the cylinders, whereby the swash plate type compressor may be quickly assembled, and the quality of the product may be appropriately maintained.